one very personal thought (and i might have said this here before, but, you know, with old age, you tend to forget

sorry if i'm repeating myself):
best way i know to get rid of performance nerves: get to love your audience, love the work you're playing, and keep in mind as you're walking on the stage that you are there only to get all these wonderful people to get to know this wonderful work/composer. as pianist, you are nothing more than a story teller - the story's already written, now all you have to do is tell it so that everybody will love it.
(imho)